Industrial dispensers for toweling are primarily designed to dispense either a continuous length of web material, folded paper towels, or rolls of paper towels. Continuous towels are generally made of a reusable material and form a towel loop outside of the dispenser cabinet for the consumer to use. Folded towels are paper towels which are pre-cut and folded into various configurations to be individually dispensed for use. Roll towels are continuous rolls of paper toweling which are wound around a cardboard core and which are, upon dispensing, separated into and delivered as individual lengths of material.
Continuous web dispensers, such as those disclosed in U.S. Pat. No. 2,930,663 to Weiss and U.S. Pat. No. 3,858,951 to Rasmussen, require the user to pull on the loop of exposed toweling in order to cause a length of clean toweling to be dispensed and the exposed soiled toweling to be correspondingly taken up within the dispenser. Although economical, the continuous exposure of the soiled toweling is deemed unsightly, and therefore unacceptable to many consumers when compared to the many available alternatives. Further, the exposure and possible reuse of soiled toweling may present additional health hazards and sanitation concerns which should be avoided.
The use of either interfolded paper towels or C-fold paper towels eliminates the potential health risks associated with continuous web toweling. Dispensers for folded paper towels allow a user to pull the exposed end of a new individual towel in order to dispense the towel. These dispensers, such as the one disclosed in U.S. Pat. No. 3,269,592 to Slye et al., are also easy to refill with folded towels. That is, when the dispenser is partially empty, the cover can simply be removed and the remaining stack of towels can be replenished through the open top. Folded towels are, however, not usually the most economical alternative for institutional or other high-volume situations.
Roll towels are cheaper to manufacture than folded towels and also eliminate the potential health and sanitation problems associated with continuous web toweling systems. Dispensers for roll towels usually include a lever, crank, or other user-activated mechanism for dispensing a length of towel and a blade for then severing the length of towel from the remaining roll. In contrast to folded towels, however, there is no way to simply replenish a partially depleted roll of web material in a roll dispenser. In some prior an dispensers, a new roll must be substituted thereby resulting in the waste of the partially depleted roll, or "stub" roll. To overcome the problem of stub roll waste, roll dispensers have been designed to dispense two rolls of web material sequentially such that upon depletion of a primary roll, feeding from a reserve roll is commenced. Prior an systems have accomplished this transfer by either modifying the end of the web material or modifying the roll core upon which the web material is wound, such as the system disclosed in U.S. Pat. No. 3,288,387 to Craven, Jr. Alternatively, the system of U.S. Pat. No. 3,628,743 to Bastian et al. senses the diameter of the primary roll in order to activate the transfer to the reserve roll and the system of U.S. Pat. No. 3,917,191 to Graham, Jr. et al. senses the tension in the primary roll in order to detect when it is nearly exhausted. Unfortunately, tension responsive transfers are not particularly reliable since conditions other than reaching the end of roll can trigger their operation, such as the slackening of the web or a break in the web material. Diameter responsive transfers also have their drawback in that the reserve web begins dispensing prior to the complete exhaustion of the primary roll. Thus, for a short time web material is dispensed simultaneously from both rolls and again results in a waste of material.
To overcome these disadvantages, the systems of U.S. Pat. No. 4,165,138 to Hedge et al. and U.S. Pat. No. 4,378,912 to Perrin et al. provide a transfer mechanism which is based on the feed rolls themselves. These systems utilize a transfer mechanism which senses the absence or presence of paper from around a grooved feed roll by using a sensing finger which rides along the top surface of the web material and which then drops down into the groove in the feed roll when the trailing end of the primary web has passed thereover and thus uncovers the groove. Responsive to the movement of the sensing finger into the groove, the reserve web is introduced into the feed nip between the feed rolls and dispensing from the reserve roll begins. This type of transfer mechanism generally eliminates the false transfer associated with tension responsive systems and reduces the amount of double sheet dispensing which occurs in other prior art diameter and end of roll responsive systems. The use of sensing fingers on the web material, however, produces extra friction which can inadvertently tear the web and the introduction of additional components to sense the absence of the web and transfer the reserve web to between the feed rollers creates even more opportunities for a transfer failure to occur.
A strong need therefore has existed for a flexible sheet dispenser having an automatic transfer mechanism which substantially eliminates the simultaneous dispensing from both primary and reserve rolls, which requires few additional parts within the dispenser and which does not obstruct the proper dispensing of either the primary or reserve web material.